. >> reporter: pistorius claims he thought an intruder was in the home, said he acted in self-defense. abc's "20/20" built a replica of the crime scene to examine crucial evidence at the scene. >> prosecutors say what were two cell phones doing there? >> it would imply an argument. >> she just got up in the middle of the night to go to the bathroom and somehow brought two cell phones with her to leave outside the toilet? they say it doesn't make any sense at all. >> reporter: the trial is set down for three weeks, but the prosecutors alone are calling more thundr witnesses, so it's expected to run much longer. right up until the moments before this trial, prosecutors had been waiting on hel unlock crucial data encrypted on pistorius'e. they now have that and say they're confident of securing a guilty verdict. david. >> hamish macdonald on the s hamish, thank you. eton all e o difference hours make. e plasti the giant ake. oscar statue. as we mentioned a moment umbrellas till handy but hopefully though weather surprises. and lara spencer is there for us. take it away. >> reporter: good